Problem: $ { \left[\begin{array}{r}{3} \\ {-1} \\ {1}\end{array}\right]+\left[\begin{array}{r}{1} \\ {0} \\ {-2}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{r}{3}+{1} \\ {-1}+{0} \\ {1}+{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{4} \\ {-1} \\ {-1}\end{array}\right]}$